(I) Field of the Invention:
The present invention relates to a medical utensil and more particularly to one in which the portion which contacts body fluid or liquid medicine is formed of synthetic resin.
(II) Description of the Prior Art
In the medical field, synthetic resins are used to form medical utensils requiring transparency or flexibility such as blood bags, fluid supply bags, catheters, tubes and the like. Known synthetic resins for such use are polyvinyl chloride or a blend of polyvinyl chloride with polyurethane, polybutadiene or polyacrylonitrile, and the like. Unfortunately, these conventional synthetic resins fail to completely satisfy the requirements for the medical utensil.
The requirements for the material of medical utensil are: (1) The material must not be attacked by body fluid or liquid medicine contacting it; (2) It must have a low permeability of water vapor or other gases; (3) It must have high heat-resistance since it is subjected to a high vapor pressure sterilization. In addition, it must have a high fusibility by heating, particularly high frequency heating, from a molding view point.
Polyvinyl chloride which is currently most widely used for the medical utensil material contains a plasticizer for imparting flexibility, a heat stabilizer for imparting heat stability, lubricant for improving the molding characteristic, and the like. When it contacts body fluid or liquid medicine, these additive agents are likely to elute from the material. This is undesirable in medical utensils. This material also has a low heat-resistance. Also, the above-mentioned blends are unsatisfactory in flexibility, transparency, and compatibility. In addition they exhibit poor heat-resistance.
Further, the above-mentioned synthetic resins have a relatively high permeability to vapor or gases. Accordingly, liquid medicine in the container made of such resins tends to change its composition due to vapor and its quality due to oxidation.